For soil-working tools, such as ploughs, harrows, subsoilers (soil decompactors), seed drills, dippers or grabs for excavators, one used to either weld new end bits onto them or to replace screwed-on end bits when one or more end bits of the tool had been worn down.
For such tools, reversible end bits or reversible wear parts are known. The advantage of being able to reverse a wear part is that the longevity of the wear part is thereby prolonged.
To make it easy and fast to reverse such reversible end bit, numerous attempts have been made to provide some kind of “Knock On-Knock Off” system enabling attachment of a wear part to a holder by some kind of wedging connection.
Such attachment of a replaceable wear part is known from EP 1 259 105 B2. There, the wear part is attached to a leading edge of a working tool in that wear part and leading edge on a working tool have co-operative guide formations extending generally perpendicular to the leading edge and which provide an inter-fitting wedging connection for engagement of the wear part on the working tool.
Therein, those guide formations are defined by walls or faces which are each of V-shape in cross-section and configured to oppose rotation of the wear part about its longitudinal axis.
It is a drawback of such V-shape that, if the “male” and the “female” parts do not inter-fit completely, in case eg a burr or the like should be present on just one of the faces, or if a hard object should become wedged between two faces intended for resting against each other, one would experience that the intended interface contact is not established, but rather a pointwise contact, which may entail that the wear part is not attached in a reliable manner.
That can be seen e.g., by the wear part being, when it is no longer exposed to an influence from the soil to the effect that the wear part is pressed into its wedge-shaped bed, at risk of falling off the working tool when the latter is taken from e.g., one plot of land to another.
From GB 641 825 A is known a changeable/renewable point (cap) for a plough share. The cap is held in place by means of a grub screw. Further the cap is retained in position by a metal strap. One end of the strap is looped around an anchorage in the cap and the other end of the strap is attached to the frog or other part of the plough by a fastener means such as, for example, a bolt passing through a hole in the other end of the strap.
GB 641 825 A also discloses that the cap at its trailing edge is provided with one or more openings that is/are oriented rearwardly relative to the end bit and for receiving coupling means from a holder part.
From GB 678 382 A is known a holder part for retaining a point by friction, where the holder part is provided with a pair of protruding coupling means, which protruding coupling means are provided with a space, where the distance between the two protruding coupling means is reduced with the distance from their end faces.
The point and the holder part are provided with v-shaped as well as D-shaped (rounded) surfaces for engagement. A pin is inserted between the point and the holder part in order to retain the point in the holder part during use of the plough.